Substrate processing method and substrate processing apparatus

Abstract

This substrate processing method comprises: preparing a substrate having a first main surface and a second main surface facing away from the first main surface, and having a slice mark on the first main surface; and supplying an etchant containing hydrofluoric acid and nitric acid to the first main surface to reveal the slice mark on the first main surface.

Description

Substrate processing method and substrate processing apparatus

[0001] This disclosure relates to a substrate processing method and a substrate processing apparatus.

[0002] Patent Document 1 describes a method for processing semiconductor wafers. This processing method involves applying a chamfering process, a lapping process, an etching process, and a mirror polishing process to a semiconductor wafer obtained by slicing a single crystal ingot. The etching process includes alkaline etching and acid etching in that order. A mixed acid is used for acid etching. The mixed acid includes hydrofluoric acid, nitric acid, phosphoric acid, and water.

[0003] Japanese Patent Application Publication No. 2002-203823

[0004] One embodiment of the present disclosure provides a technology that can accurately measure the position of the raised portion of a slice mark on a substrate.

[0005] A substrate processing method according to one embodiment of the present disclosure comprises preparing a substrate having a first main surface and a second main surface facing the opposite direction to the first main surface, and having slice marks on the first main surface, and supplying an etching solution containing hydrofluoric acid and nitric acid to the first main surface to make the slice marks on the first main surface visible.

[0006] According to one embodiment of the present disclosure, the position of the raised portion of the slice mark on the substrate can be measured with high accuracy.

[0007] Figure 1 is a flowchart showing an example of a substrate processing method. Figure 2 is a cross-sectional view showing an example of step S101. Figure 3 is a plan view showing an example of step S101. Figure 4 is a cross-sectional view showing an example of step S102. Figure 5 is a cross-sectional view showing an example of the action of the etching solution. Figure 6 is a cross-sectional view showing an example of the flow of the etching solution. Figure 7 is a diagram showing an example of experimental data. Figure 8 is a diagram showing another example of experimental data. Figure 9 is a cross-sectional view showing an example of step S104. Figure 10 is a cross-sectional view showing an example of step S106. Figure 11 is a cross-sectional view showing an example of step S108. Figure 12 is a plan view showing an example of a substrate processing apparatus.

[0008] Embodiments of this disclosure will be described below with reference to the drawings. In each drawing, identical or similar components are denoted by the same reference numerals, and their descriptions may be omitted. In this specification, the X-axis, Y-axis, and Z-axis directions are perpendicular to each other, the X-axis and Y-axis directions are horizontal, and the Z-axis direction is vertical.

[0009] The X-axis direction includes the positive X-axis direction and the negative X-axis direction, which is the opposite direction to the positive X-axis direction. The Y-axis direction includes the positive Y-axis direction and the negative Y-axis direction, which is the opposite direction to the positive Y-axis direction. The Z-axis direction includes the positive Z-axis direction and the negative Z-axis direction, which is the opposite direction to the positive Z-axis direction. The positive Z-axis direction is upward, and the negative Z-axis direction is downward.

[0010] An example of a substrate processing method will be described with reference to Figures 1 to 11. The substrate processing method includes steps S101 to S108, as shown in Figure 1, for example. Steps S101 to S108 are performed under the control of a control circuit. Polishing may be performed instead of grinding.

[0011] Note that the substrate processing method does not necessarily have to include all of the steps S101 to S108 shown in Figure 1. The substrate processing method only needs to include at least steps S101 to S102, and does not need to include steps S103 to S108.

[0012] Furthermore, the substrate processing method may include additional steps not shown. One example of an unshown step is cleaning the substrate. Cleaning the substrate is performed, for example, immediately after steps S104, S106, or S108. Both cleaning and etching may be performed immediately after steps S104, S106, or S108.

[0013] Step S101 involves preparing the substrate W as shown in Figure 2. Preparing the substrate W involves, for example, loading the substrate W into the substrate processing apparatus 1 shown in Figure 12. The substrate W is loaded into the substrate processing apparatus 1 while housed in a cassette C.

[0014] The substrate W is a silicon wafer or a compound semiconductor wafer. The compound semiconductor wafer is not particularly limited, but examples include a GaAs wafer, a SiC wafer, a GaN wafer, or an InP wafer. The substrate W is a bare wafer. The substrate W is, for example, disc-shaped. The substrate W may have a bevel around its periphery.

[0015] As shown in Figure 2, the substrate W includes a first main surface Wa and a second main surface Wb facing the opposite direction to the first main surface Wa. The substrate W has slice marks Wc on both the first main surface Wa and the second main surface Wb. The slice marks Wc are stripe-like marks that occur when a single crystal ingot is sliced ​​into multiple substrates W using a wire saw.

[0016] As shown in Figures 2 and 3, the slice marks Wc have alternating convex ridges Wc1 and concave ridges Wc2 in the ingot feeding direction (positive X-axis direction in Figures 2 and 3). The pitch of the convex ridges Wc1 is not particularly limited, but is, for example, 0.5 mm to 5 mm. In Figure 3, the convex ridges Wc1 are perpendicular to the ingot feeding direction, but they may be curved.

[0017] The pitch of the protruding ridge Wc1 is determined by the wire diameter, wire feed speed, wire reciprocating speed, ingot feed speed, and abrasive particle size. In the slicing device, the wire is fed from the first bobbin and wound onto the second bobbin while reciprocating. However, the wire may only travel in one direction. The abrasive particles are, for example, free abrasive particles contained in the slurry. The abrasive particles may also be fixed abrasive particles fixed to the wire.

[0018] The substrate W has minute protrusions Wd1 and minute depressions Wd2 in addition to the slice marks Wc. The minute protrusions Wd1 and minute depressions Wd2 are formed on the side or bottom surface of the recessed portion Wc2, or on the top surface of the convex portion Wc1. The minute protrusions Wd1 and minute depressions Wd2 can become noise when measuring the position of the convex portion Wc1 of the slice marks Wc. Therefore, in this embodiment, the noise is removed in step S102.

[0019] Step S102 includes supplying an etching solution L to a first main surface Wa of a substrate W as shown in FIG. 4. The etching solution L contains hydrofluoric acid (HF) and nitric acid (HNO ３ 3). The substrate W is oxidized by nitric acid, and the oxide is removed by hydrofluoric acid. When the substrate W is a silicon wafer, etching is considered to proceed according to the following chemical reaction formulas (1) and (2). (1) Si + 4HNO ３ 3 → 3SiO ２ 2 + 4NO + 2H ２ 2O (2) SiO ２ 2 + 6HF → H ２ 2SiF ６ 6 + 2H ２ 2O Note that not only nitric acid but also nitrous acid (HNO ２ 2) also oxidizes the substrate W.

[0020] The etching solution L reveals slice marks Wc. Revealing the slice marks Wc includes, as shown in FIG. 5, leaving the slice marks Wc, selectively removing micro-protrusions Wd1 compared to micro-depressions Wd2, and reducing surface roughness. Surface roughness is represented by arithmetic average roughness Ra. The arithmetic average roughness Ra is measured in accordance with JIS B 0601:2013. A cutoff value λf is set according to the pitch of the convex streaks Wc1 so that the arithmetic average roughness Ra does not include height fluctuations caused by the slice marks Wc.

[0021] With reference to FIG. 6, an example of the action of the etching solution L will be described. In FIG. 6, illustration of the slice marks Wc is omitted. The flow of the etching solution L stagnates in the micro-depressions Wd2. Compared with the micro-protrusions Wd1, the supply of hydrofluoric acid and nitric acid to the micro-depressions Wd2 is insufficient, and the etching rate is slower. Therefore, the micro-protrusions Wd1 can be selectively removed compared to the micro-depressions Wd2.

[0022] As shown in FIG. 5, the height of the micro-protrusions Wd1 and the depth of the micro-depressions Wd2 are smaller than the average value of the height difference between adjacent convex streaks Wc1 and concave streaks Wc2. Therefore, the etching solution L can selectively remove the micro-protrusions Wd1 compared to the micro-depressions Wd2 while leaving the slice marks Wc. Note that, unlike the slice marks Wc, the micro-protrusions Wd1 and the micro-depressions Wd2 do not have periodicity.

[0023] By extending the etching time in step S102, it is possible to remove the slice marks Wc with the etching solution L. However, the etching time becomes too long. This is because the height difference between adjacent convex portions Wc1 and concave portions Wc2 is large compared to the height of the minute protrusions Wd1 and the depth of the minute depressions Wd2. Therefore, in this embodiment, instead of removing the slice marks Wc, the slice marks Wc are made visible. The visible slice marks Wc are removed by irradiation with a laser beam. This improves throughput.

[0024] An example of experimental data will be explained with reference to Figure 7. In Figure 7, the substrate W was obtained by slicing a silicon single crystal ingot with a wire saw, and each of the first main surface Wa and the second main surface Wb had slice marks Wc, minute protrusions Wd1, and minute depressions Wd2. In the experiment shown in Figure 7, L1 and L3 were used as etching solutions L. Etching solution L3 was substantially composed of HF and HNO ３ and H ２ It contains only O, and is essentially HPO ３ Unlike the other, etching solution L1 contains HF and HNO ３ and H ２ In addition to O, HPO ３ Includes.

[0025] As shown in Figure 7, when the etching solution L3 was supplied to the first main surface Wa, the arithmetic mean roughness Ra of the first main surface Wa decreased as the amount of etching of the first main surface Wa increased. This indicates that the minute protrusions Wd1 could be selectively removed compared to minute depressions Wd2 while leaving the slice marks Wc, and the slice marks Wc could be made visible. The visibility of the slice marks Wc could also be confirmed visually. Specifically, the striped pattern shown in Figure 3 could not be visually observed on the silicon wafer before etching, whereas the striped pattern could be visually observed on the silicon wafer after etching.

[0026] On the other hand, when etching solution L1 was supplied to the first main surface Wa, even if the etching amount of the first main surface Wa increased, the arithmetic mean roughness Ra of the first main surface Wa did not decrease, but rather increased. ３If it contains HF and HNO, the viscosity of etching solution L1 is high, so ３ This is thought to be because the etching solution L1 was sufficiently supplied to the minute depressions Wd2 shown in Figure 6. When the etching solution L1 was supplied to the first main surface Wa, the silicon wafer after etching did not show any visible stripe-like patterns, similar to the silicon wafer before etching.

[0027] Referring to Figure 8, another example of experimental data will be described. In Figure 8, the substrate W was obtained by slicing a silicon single crystal ingot with a wire saw and then grinding it. The first main surface Wa and the second main surface Wb each had minute protrusions Wd1 and minute depressions Wd2, but no slice marks Wc. In the experiment shown in Figure 7, L2 to L5 were used as etching solutions L. Etching solutions L2 to L5 were substantially composed of HF and HNO ３ and H ２ It contains only O, and is essentially HPO ３ It does not include.

[0028] When etching solutions L2 to L4 were supplied to the first main surface Wa, the arithmetic mean roughness Ra of the first main surface Wa decreased as the amount of etching on the first main surface Wa increased. This indicates that minute protrusions Wd1 could be selectively removed compared to minute depressions Wd2, and the first main surface Wa could be made mirror-finished. The mirror-finishing of the first main surface Wa could also be confirmed visually. However, when etching solution L2 was supplied to the first main surface Wa, white smoke was generated. If the generation of white smoke became severe, the substrate W would discolor.

[0029] On the other hand, when etching solution L5 was supplied to the first main surface Wa, even when the amount of etching on the first main surface Wa increased, the arithmetic mean roughness Ra of the first main surface Wa did not decrease, but rather increased. When etching solution L5 was supplied to the first main surface Wa, the silicon wafer after etching could not be visually confirmed to be mirror-like, just like the silicon wafer before etching.

[0030] From the experiments shown in Figures 7 and 8, it is preferable that the etching solution L contains 2.5% to 8.0% by volume of hydrofluoric acid, 60.0% to 65.0% by volume of nitric acid, and 32.0% to 34.0% by volume of water. If the composition of the etching solution L is within the above range, the viscosity of the etching solution L is appropriately low, the minute protrusions Wd1 are more easily etched than the minute depressions Wd2, and the slice marks Wc can be made visible. In addition, if the composition of the etching solution L is within the above range, the generation of white smoke can be suppressed and discoloration of the substrate W can be suppressed.

[0031] Referring again to Figure 4, an example of the etching apparatus 34 will be described. As shown in Figure 4, the etching apparatus 34 is a single-wafer type and etches one substrate W at a time. However, although not shown, the etching apparatus 34 may be a batch type and multiple substrates W may be immersed in the etching solution L simultaneously.

[0032] The etching apparatus 34 includes a processing container 341. A gate G and a gate valve V for opening and closing the gate G are provided on the side wall of the processing container 341. The substrate W is fed into the processing container 341 through the gate G. Next, the substrate W is processed with etching solution L inside the processing container 341. After that, the substrate W is discharged to the outside of the processing container 341 through the gate G. The processing container 341 houses a substrate holder 342, a nozzle 344, a cup 347, and the like inside.

[0033] The etching apparatus 34 includes a substrate holding section 342. The substrate holding section 342 holds the substrate W horizontally with the first main surface Wa of the substrate W facing upward. The substrate holding section 342 has, for example, claw portions 342a that hold the outer periphery of the substrate W. Multiple claw portions 342a are provided at equal intervals in the circumferential direction of the substrate W. Although not shown, the substrate holding section 342 may also use vacuum suction to hold the lower surface of the substrate W.

[0034] The etching apparatus 34 includes a rotating section 343. The rotating section 343 rotates the substrate holder 342, thereby rotating the substrate W together with the substrate holder 342. The rotating section 343 includes a rotating motor and a transmission mechanism that transmits the rotational driving force of the rotating motor to the substrate holder 342. The transmission mechanism includes, for example, a combination of a pulley and a timing belt, or a combination of multiple gears.

[0035] The etching apparatus 34 includes a nozzle 344. The nozzle 344 supplies an etching solution L onto a substrate W. For example, the nozzle 344 supplies the etching solution L to an upper surface of the rotating substrate W. The nozzle 344 supplies the etching solution L and a rinsing solution onto the substrate W in this order. The rinsing solution is pure water such as DIW (deionized water). The etching solution L and the rinsing solution may be supplied by separate nozzles 344.

[0036] The nozzle 344 is connected to a liquid supply unit 345. The liquid supply unit 345 prepares the etching solution L by mixing, for example, a hydrofluoric acid aqueous solution and a nitric acid aqueous solution at a desired ratio, and supplies the etching solution L to the nozzle 344. The liquid supply unit 345 includes a tank for storing the etching solution L, an opening-closing valve for opening and closing a flow path of the etching solution L, a flow rate control valve for adjusting a flow rate of the etching solution L, and the like.

[0037] The etching apparatus 34 includes a nozzle moving unit 346. The nozzle moving unit 346 moves the nozzle 344 in a horizontal direction. For example, the nozzle moving unit 346 moves the nozzle 344 in a radial direction of the substrate W. The nozzle moving unit 346 includes, for example, an arm 346a that holds the nozzle 344, and a drive unit 346b that turns the arm 346a.

[0038] The etching apparatus 34 includes a cup 347. The cup 347 surrounds an outer circumference of the substrate W held by a substrate holding unit 342, and collects the etching solution L and the rinsing solution scattered from the outer circumference of the substrate W. A drain pipe 348 and an exhaust pipe 349 are provided at a bottom of the cup 347. The drain pipe 348 discharges the etching solution L and the rinsing solution accumulated inside the cup 347. The exhaust pipe 349 discharges gas accumulated inside the cup 347.

[0039] As will be described later, it may not be determined until step S103 which side of the substrate W will become the first main surface Wa. In that case, in step S102, the etching solution L can be supplied sequentially to both sides of the substrate W to make the slice marks Wc on both sides visible. It is also possible to supply the etching solution L to both sides of the substrate W simultaneously. The substrate W can then be immersed in the etching solution L.

[0040] Step S103 involves measuring the surface shape of the first principal surface Wa. The surface shape of the first principal surface Wa is represented, for example, by a height distribution from a reference plane. The reference plane is a plane. The reference plane is, for example, a plane obtained by approximating the center plane of the first principal surface Wa and the second principal surface Wb using the least squares method. The reference plane may be a crystal plane represented by a desired Miller index, or a plane inclined by a desired off-angle from that crystal plane.

[0041] The surface shape of the first main surface Wa is measured using a surface shape measuring device. The surface shape measuring device is not particularly limited as long as it has a resolution narrower than the pitch of the protrusions Wc1, but it is preferably optical. Examples of optical devices include confocal, laser interferometry, or triangulation. The control circuit 9 acquires the measurement data from the surface shape measuring device.

[0042] According to this embodiment, the slice marks Wc are made visible before step S103. Since minute protrusions Wd1 and minute depressions Wd2 that cause noise when measuring the position of the protruding portion Wc1 are removed before step S103, the position of the protruding portion Wc1 can be measured with high accuracy.

[0043] In step S103, the surface shapes of both sides of the substrate W, one side and the opposite side, may be measured. The surface with the smallest average difference in height between adjacent convex portions Wc1 and concave portions Wc2 can be set as the first main surface Wa, thereby shortening the processing time in step S104.

[0044] Step S104 involves removing slice marks Wc from the first main surface Wa by irradiating it with a laser beam LB based on the measurement data from step S103, as shown in Figure 9. Removing slice marks Wc includes reducing the height difference between adjacent convex portions Wc1 and concave portions Wc2.

[0045] The laser beam LB selectively irradiates the convex ridges Wc1, selectively removing them. This reduces the amount of material removed compared to using lapping to remove slice marks Wc. This is because lapping removes concave ridges Wc2 simultaneously with removing convex ridges Wc1. Also, lapping uses water, whereas laser processing does not. However, laser processing and lapping can be combined, as long as the amount of lapping can be reduced.

[0046] The laser beam LB ablates the first main surface Wa. At the irradiation point P of the laser beam LB, the substrate W locally changes state from solid to gas and scatters, or scatters while remaining in the solid state, and the substrate W is locally abraded.

[0047] The wavelength of the laser beam LB is set appropriately according to the material of the substrate W. When the substrate W is a silicon wafer, the wavelength of the laser beam LB is preferably 500 nm to 1200 nm.

[0048] The center of the irradiation point P of the laser beam LB is positioned at the apex of the protruding portion Wc1. The spot diameter (diameter) of the irradiation point P of the laser beam LB is preferably less than or equal to the pitch of the protruding portion Wc1. The spot diameter of the irradiation point P of the laser beam LB is, for example, 0.1 mm to 10 mm.

[0049] The scanning direction of the irradiation point P of the laser beam LB is, for example, along the convex ridge Wc1 (for example, in the Y-axis direction). The convex ridges Wc1 are removed one by one. However, the scanning direction of the irradiation point P of the laser beam LB may be perpendicular to the direction along the convex ridge Wc1, or diagonally intersecting the longitudinal direction of the convex ridge Wc1.

[0050] According to this embodiment, as described above, the measurement accuracy of the position of the protruding portion Wc1 is good. Therefore, the laser beam LB can be accurately irradiated onto the position of the protruding portion Wc1. Consequently, the slice marks Wc can be removed accurately. Furthermore, after the removal of the slice marks Wc, no minute protrusions Wd1 and minute depressions Wd2 remain on the first main surface Wa, resulting in a low surface roughness of the first main surface Wa.

[0051] Referring to Figure 9, an example of a laser processing apparatus 36 will be described. The laser processing apparatus 36 comprises a substrate holder 361, a light source 362, and a galvanometer scanner 363. The laser processing apparatus 36 may further include an fθ lens 364, a homogenizer 365, and an aperture 366. The fθ lens 364, homogenizer 365, and aperture 366 may be in any configuration or not.

[0052] The substrate holding portion 361 holds the substrate W. For example, the substrate holding portion 361 holds the substrate W horizontally from below with the first main surface Wa of the substrate W facing upwards. The substrate holding portion 361 holds the substrate W in a natural state without any external forces acting on it other than gravity and its counterforce, without using suction. However, the substrate holding portion 361 may use suction to hold the substrate W. The substrate holding portion 361 may be a vacuum chuck or an electrostatic chuck.

[0053] The light source 362 emits a laser beam LB. When the substrate W is a silicon wafer, the laser beam LB is, for example, infrared light. At the irradiation point P of the laser beam LB, the substrate W locally changes state from solid to gas and scatters, or scatters while remaining in the solid phase, and the substrate W is locally abraded. The laser beam LB may be focused and irradiated onto the upper surface of the substrate W. In this embodiment, the irradiation point P is the focal point where the power density is highest, but it does not have to be the focal point.

[0054] The light source 362 is, for example, a pulsed laser. The irradiation time per pulse is, for example, 30 nsec or less. If the irradiation time per pulse is 30 nsec or less, a laser beam LB with a high power density can be irradiated onto the substrate W in a short time, and overheating of the substrate W can be suppressed. Therefore, thermal degradation of the substrate W can be suppressed, and for example, the occurrence of a discolored layer can be suppressed. Preferably, the irradiation time per pulse is 10 psec or less. If the irradiation time per pulse is 10 psec or less, thermal degradation of the substrate W can be suppressed even if multiple irradiation points P are formed in the same location.

[0055] The galvanometer scanner 363 is positioned, for example, above the substrate W held by the substrate holder 361. The galvanometer scanner 363 allows the irradiation point P of the laser beam LB to be moved on the upper surface of the substrate W without moving the substrate holder 361. Even if the substrate holder 361 does not attract the substrate W, as long as the substrate holder 361 does not move, no misalignment of the substrate W relative to the substrate holder 361 occurs. Therefore, the position of the irradiation point P can be controlled with high precision.

[0056] The galvanometer scanner 363 includes two sets of galvanometer mirrors 367 and galvanometer motors 368 (only one set is shown in Figure 9). One galvanometer motor 368 rotates one galvanometer mirror 367, displacing the illumination point P in the X-axis direction. Another galvanometer motor 368 rotates another galvanometer mirror 367, displacing the illumination point P in the Y-axis direction.

[0057] The galvanometer scanner 363 is an example of a moving unit that moves the irradiation point P. The moving unit may move the substrate holder 361 in the X-axis and Y-axis directions, and may also have a motor and a ball screw mechanism that converts the rotational motion of the motor into linear motion of the substrate holder 361. The moving unit may also have a mechanism that rotates the substrate holder 361 around a vertical axis.

[0058] The fθ lens 364 forms a focal plane perpendicular to the Z-axis direction. While the galvanometer scanner 363 moves the position of the illumination point P in the X-axis direction or the Y-axis direction, the fθ lens 364 maintains the shape and dimensions of the illumination point P on the upper surface of the substrate W. In this embodiment, the height of the illumination point P coincides with the height of the focal plane, but it does not have to coincide with the height of the focal plane, and it may be higher or lower than the height of the focal plane.

[0059] The homogenizer 365 converts the power density distribution of the laser beam LB from a Gaussian distribution to a top-hat distribution, thereby homogenizing the power density. The aperture 366 shapes the cross-sectional shape of the laser beam LB into a rectangle. The aperture 366 is a light-shielding film with a rectangular opening. This opening allows the portion of the laser beam LB with a constant power density to pass through. The homogenizer 365 and aperture 366 together can form a rectangular irradiation point P with a uniform power density.

[0060] Step S105 involves inverting the substrate W. Step S105 involves inverting the substrate W so that the first main surface Wa of the substrate W faces downwards and the second main surface Wb of the substrate W faces upwards.

[0061] Step S106 involves grinding the second main surface Wb with a grinding wheel 382 while the first main surface Wa is adsorbed to the substrate holding part 381, as shown in Figure 10, after irradiation with the laser beam LB (step S104). If the substrate holding part 381 adsorbs the first main surface Wa while the first main surface Wa has slice marks Wc, the first main surface Wa will be flattened to conform to the adsorption surface 381a of the substrate holding part 381. If the second main surface Wb is ground parallel to the first main surface Wa in that state, and then the adsorption of the substrate W is released, not only will the first main surface Wa return to the state with slice marks Wc, but the slice marks Wc of the first main surface Wa will also be transferred to the second main surface Wb. In this embodiment, the second main surface Wb is ground while the first main surface Wa, from which the slice marks Wc have been removed in step S104, is adsorbed to the substrate holding portion 381, thereby suppressing the transfer of slice marks Wc. Alternatively, polishing may be performed instead of grinding. Grinding uses fixed abrasive grains, while polishing uses free abrasive grains. Polishing includes lapping.

[0062] Step S107 involves inverting the substrate W. Step S107 involves inverting the substrate W so that the first main surface Wa of the substrate W faces upward and the second main surface Wb of the substrate W faces downward.

[0063] Step S108 involves grinding the first main surface Wa with a grinding wheel 382 while the second main surface Wb is held in place by the substrate holding part 381, as shown in Figure 11, after grinding the second main surface Wb (step S106). This allows the processing quality of the first main surface Wa and the second main surface Wb to be equivalent. Since the slice marks Wc have already been removed from the first main surface Wa, the amount of grinding on the first main surface Wa may be less than the amount of grinding on the second main surface Wb. The amount of grinding on the first main surface Wa is corrected based on the etching amount in step S102. The corrected grinding amount is the value obtained by subtracting the etching amount from the grinding amount before correction. Alternatively, instead of correcting the grinding amount of the first main surface Wa, the grinding amount of the second main surface Wb may be corrected. Even if the etching amount in step S102 fluctuates, it is sufficient that the thickness of the substrate W after step S108 reaches the target value. Also, polishing may be performed instead of grinding.

[0064] An example of the substrate processing apparatus 1 will be described with reference to Figure 12. The substrate processing apparatus 1 performs steps S101 to S108 shown in Figure 7. Steps S105 to S108 may be performed outside the substrate processing apparatus 1. Also, a polishing device may be provided instead of the grinding device 38. The grinding device 38 and the polishing device are collectively referred to as the processing apparatus.

[0065] As shown in Figure 12, the substrate processing apparatus 1 includes a control circuit 9. The control circuit 9 is, for example, a computer and includes an arithmetic unit 91 such as a CPU (Central Processing Unit) and a storage unit 92 such as memory. The storage unit 92 stores programs that control various processes executed in the substrate processing apparatus 1.

[0066] The control circuit 9 controls the operation of the substrate processing apparatus 1 by causing the calculation unit 91 to execute a program stored in the memory unit 92. A lower-level control circuit is provided for each device that makes up the substrate processing apparatus 1 to control the operation of that device, and a higher-level control circuit may be provided to comprehensively control multiple lower-level control circuits. The control circuit 9 may be composed of a lower-level control circuit and a higher-level control circuit.

[0067] The control circuit 9 includes electronic circuits such as a CPU, GPU (Graphics Processing Unit), FPGA (Field Programmable Gate Array), or ASIC (Application Specific Integrated Circuit), and performs various control operations described in this specification by executing instruction codes stored in memory or by designing the circuit for special applications.

[0068] As shown in Figure 12, the substrate processing apparatus 1 comprises an input / output station 2 and a processing station 3. The input / output station 2 and the processing station 3 are arranged in this order, from the negative side in the X-axis direction to the positive side in the X-axis direction.

[0069] The loading / unloading station 2 comprises a mounting table 20, a second transport area 21, and a second transport device 22. Multiple cassettes C are placed on the mounting table 20. Each cassette C contains multiple substrates W. Multiple substrates W cut from a single crystal ingot are stored in the same cassette C. The number of cassettes C is not particularly limited.

[0070] The second transport area 21 is adjacent to the mounting table 20 and the transition device 33 of the processing station 3. The second transport device 22 transports substrates between multiple devices adjacent to the second transport area 21. The second transport device 22 has a transport arm for holding the substrate W and a drive unit for moving or rotating the transport arm. The transport arm is capable of moving horizontally (both in the X-axis and Y-axis directions) and vertically, and rotating about the vertical axis. Multiple transport arms may be provided.

[0071] The processing station 3 includes, for example, a first transport area 31, a first transport device 32, a transition device 33, an etching device 34, a surface shape measuring device 35, a laser processing device 36, a reversing device 37, a grinding device 38, and a cleaning device 39. The arrangement and number of devices constituting the processing station 3 are not limited to those shown in Figure 12.

[0072] The first transport area 31 is adjacent to the transition device 33, the etching device 34, the surface shape measuring device 35, the laser processing device 36, the reversing device 37, the grinding device 38, and the cleaning device 39. The first transport device 32 transports substrates between multiple devices adjacent to the first transport area 31. The first transport device 32 has a transport arm for holding the substrate W and a drive unit for moving or rotating the transport arm. The transport arm is capable of moving horizontally (in both the X-axis and Y-axis directions) and vertically, and rotating about the vertical axis. Multiple transport arms may be provided.

[0073] The transition device 33 relays the substrate W between the second transport device 22 of the loading / unloading station 2 and the first transport device 32 of the processing station 3. The transition device 33 for relaying from the second transport device 22 to the first transport device 32 and the transition device 33 for relaying from the first transport device 32 to the second transport device 22 may be provided separately.

[0074] The etching apparatus 34 supplies an etching solution L containing hydrofluoric acid and nitric acid to the first main surface Wa of the substrate W, thereby making the slice marks Wc of the first main surface Wa visible. Making the slice marks Wc visible involves selectively removing minute protrusions Wd1 compared to minute depressions Wd2 while leaving the slice marks Wc, thereby reducing the surface roughness.

[0075] The surface shape measuring device 35 measures the surface shape of the first main surface Wa of the substrate W. The surface shape measuring device 35 is not particularly limited as long as it has a resolution narrower than the pitch of the protrusions Wc1, but it is preferably optical. Optical types include, for example, confocal, laser interferometry, or triangulation. The surface shape measuring device 35 preferably has an optical sensor 351. The optical sensor 351 is, for example, a displacement sensor. Displacement sensors include, for example, confocal, laser interferometry, or triangulation. The surface shape measuring device 35 transmits the measurement data to the control circuit 9. The control circuit 9 acquires the measurement data from the optical sensor 351.

[0076] The laser processing apparatus 36 removes slice marks Wc from the first main surface Wa by irradiating it with a laser beam LB based on the measurement data from the optical sensor 351. Removing slice marks Wc includes reducing the height difference between adjacent convex portions Wc1 and concave portions Wc2.

[0077] The inversion device 37 inverts the substrate W vertically. By inverting the substrate W vertically, the inversion device 37 aligns the first main surface Wa downwards and the second main surface Wb upwards. Alternatively, by inverting the substrate W vertically, the inversion device 37 aligns the first main surface Wa upwards and the second main surface Wb downwards. There may be multiple inversion devices 37, and there may be separate inversion devices 37 that align the first main surface Wa upwards and inversion devices 37 that align the second main surface Wb upwards.

[0078] The grinding device 38 grinds the second main surface Wb with the grinding wheel 382 while the first main surface Wa is held in place by the substrate holding part 381. Alternatively, the grinding device 38 grinds the first main surface Wa with the grinding wheel 382 while the second main surface Wb is held in place by the substrate holding part 381. There may be multiple grinding devices 38, and grinding devices 38 for grinding the first main surface Wa and grinding devices 38 for grinding the second main surface Wb may be provided separately.

[0079] The cleaning device 39 cleans the first main surface Wa of the substrate W. The cleaning device 39 can also clean the second main surface Wb of the substrate W. There may be multiple cleaning devices 39, and separate cleaning devices 39 may be provided for cleaning the first main surface Wa of the substrate W and for cleaning the second main surface Wb of the substrate W.

[0080] Next, the operation of the substrate processing apparatus 1 with the above configuration will be described. First, a transport device (not shown) loads the substrate W into the substrate processing apparatus 1. This prepares the substrate W (step S101). The substrate W is placed on the mounting table 20 while contained in a cassette C. Next, the second transport device 22 removes the substrate W from the cassette C on the mounting table 20 and transports it to the transition device 33. Subsequently, the first transport device 32 of the processing station 3 removes the substrate W from the transition device 33 and transports it to the etching device 34.

[0081] Next, the etching apparatus 34 supplies an etching solution L containing hydrofluoric acid and nitric acid to the first main surface Wa of the substrate W, making the slice marks Wc of the first main surface Wa visible (step S102). Making the slice marks Wc visible involves selectively removing minute protrusions Wd1 compared to minute depressions Wd2 while leaving the slice marks Wc, thereby reducing the surface roughness. After step S102, the first transport apparatus 32 removes the substrate W from the etching apparatus 34 and transports it to the surface shape measuring apparatus 35.

[0082] Next, the surface shape measuring device 35 measures the surface shape of the first main surface Wa. The optical sensor 351 of the surface shape measuring device 35 transmits the measurement data to the control circuit 9. The control circuit 9 acquires the measurement data from the optical sensor 351 (step S103). Since the slice marks Wc have been made visible in advance, the position of the raised portion Wc1 of the slice marks Wc can be measured with high accuracy. After step S103, the first transport device 32 removes the substrate W from the surface shape measuring device 35 and transports it to the laser processing device 36.

[0083] Next, the laser processing device 36 removes the slice marks Wc from the first main surface Wa by irradiating it with a laser beam LB based on the measurement data from the optical sensor 351 (step S104). Since the measurement accuracy of the position of the protrusions Wc1 is good, the laser beam LB can be accurately irradiated to the position of the protrusions Wc1. Therefore, the slice marks Wc can be removed with high accuracy. In addition, after the removal of the slice marks Wc, no minute protrusions Wd1 and minute depressions Wd2 remain on the first main surface Wa, and the surface roughness of the first main surface Wa is small. After step S104, the first transport device 32 removes the substrate W from the laser processing device 36 and transports it to the cleaning device 39.

[0084] Next, the cleaning device 39 cleans the first main surface Wa of the substrate W. After that, the first transport device 32 removes the substrate W from the cleaning device 39 and transports it to the inversion device 37.

[0085] Next, the inversion device 37 inverts the substrate W (step S105). By inverting the substrate W vertically, the inversion device 37 aligns the first main surface Wa of the substrate W downwards and the second main surface Wb of the substrate W upwards. After step S105, the first transport device 32 removes the substrate W from the inversion device 37 and transports it to the grinding device 38.

[0086] Next, the grinding device 38 grinds the second main surface Wb with the grinding wheel 382 while the first main surface Wa is held in place by the substrate holding part 381 (step S106). By grinding the second main surface Wb parallel to the first main surface Wa, from which the slice marks Wc have been removed beforehand, it is possible to suppress the transfer of the slice marks Wc from the first main surface Wa to the second main surface Wb. Polishing may be performed instead of grinding. After step S106, the first transport device 32 removes the substrate W from the grinding device 38 and transports it to the washing device 39.

[0087] Next, the cleaning device 39 cleans the second main surface Wb of the substrate W. After that, the first transport device 32 removes the substrate W from the cleaning device 39 and transports it to the inversion device 37.

[0088] Next, the inversion device 37 inverts the substrate W (step S107). By inverting the substrate W vertically, the inversion device 37 aligns the first main surface Wa of the substrate W upwards and the second main surface Wb of the substrate W downwards. After step S107, the first transport device 32 removes the substrate W from the inversion device 37 and transports it to the grinding device 38.

[0089] Next, the grinding device 38 grinds the first main surface Wa with the grinding wheel 382 while the second main surface Wb is held in place by the substrate holding part 381 (step S108). This makes the processing quality of the first main surface Wa and the second main surface Wb equivalent. Alternatively, polishing may be performed instead of grinding. After step S107, the first transport device 32 removes the substrate W from the grinding device 38 and transports it to the washing device 39.

[0090] Next, the cleaning device 39 cleans the first main surface Wa of the substrate W. Then, the first transport device 32 removes the substrate W from the cleaning device 39 and transports it to the transition device 33. Next, the second transport device 22 removes the substrate W from the transition device 33 and places it in the cassette C on the mounting table 20. Finally, a transport device (not shown) unloads the substrate W, which is now in the cassette C, from the substrate processing device 1.

[0091] The embodiments of the substrate processing method and substrate processing apparatus described above have been explained, but the disclosure is not limited to the embodiments described above. Various changes, modifications, substitutions, additions, deletions, and combinations are possible within the scope of the claims. These also naturally fall within the technical scope of the disclosure.

[0092] This application claims priority based on Japanese Patent Application No. 2025-053211, filed with the Japan Patent Office on March 27, 2025, and the entire contents of Japanese Patent Application No. 2025-053211 are incorporated herein by reference.

[0093] L Etching solution W Substrate Wa First main surface Wb Second main surface Wc Slice marks

Claims

1. A substrate processing method comprising: preparing a substrate having a first main surface and a second main surface facing the opposite direction to the first main surface, and having slice marks on the first main surface; and supplying an etching solution containing hydrofluoric acid and nitric acid to the first main surface to make the slice marks on the first main surface visible.

2. The etching solution contains 2.5% to 8.0% by volume of hydrofluoric acid (HF) and nitric acid (HNO). ３ The substrate processing method according to claim 1, comprising 60.0% to 65.0% by volume of ) and 32.0% to 34.0% by volume of water.

3. The substrate processing method according to claim 1, further comprising measuring the surface shape of the first main surface with an optical sensor after supplying the etching solution.

4. The substrate processing method according to claim 3, wherein the optical sensor is a displacement sensor.

5. The substrate processing method according to claim 3, further comprising irradiating the first main surface with a laser beam based on measurement data from the optical sensor to remove the slice marks from the first main surface.

6. The substrate processing method according to claim 5, further comprising grinding or polishing the second main surface while the first main surface is adsorbed to the substrate holding portion after irradiation with the laser beam.

7. A substrate processing apparatus comprising: a transport device for transporting a substrate having a first main surface and a second main surface facing the opposite direction to the first main surface, and having slice marks on the first main surface; and an etching device for supplying an etching solution containing hydrofluoric acid and nitric acid to the first main surface to make the slice marks on the first main surface visible.

8. The etching solution contains 2.5% to 8.0% by volume of hydrofluoric acid (HF) and nitric acid (HNO). ３ The substrate processing apparatus according to claim 7, comprising 60.0% to 65.0% by volume of ) and 32.0% to 34.0% by volume of water.

9. The substrate processing apparatus according to claim 7, further comprising a surface shape measuring device that measures the surface shape of the first main surface with an optical sensor after supplying the etching solution with the etching apparatus.

10. The substrate processing apparatus according to claim 9, wherein the optical sensor is a displacement sensor.

11. The substrate processing apparatus according to claim 9, further comprising a laser processing apparatus that removes the slice marks on the first main surface by irradiating the first main surface with a laser beam based on measurement data from the optical sensor.

12. The substrate processing apparatus according to claim 11, further comprising a processing apparatus that grinds or polishes the second main surface while the first main surface is held in place by adsorption to the substrate holding portion after irradiating it with the laser beam using the laser processing apparatus.

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